Infusion system with air-in-line clear function

ABSTRACT

An infusion system with an air-in-line sensor is provided with improved apparatus and method for quickly and easily clearing small quantities of undissolved gas such as air from the sensor detection field. The infusion system includes an infusion pump having control components responsive to the air-in-line sensor to activate an alarm and/or to cease pump operation when undissolved gas is detected. A &#34;clear air&#34; key or switch is provided on the pump for actuation by medical personnel to operate the pump in a manner delivering a small pulse of the infusion liquid to move a small detected quantity of gas past the air-in-line sensor. The system can be adapted for actuation of the &#34;clear air&#34; key up to a selected number of times, while monitoring and accumulating the total fluid quantity delivered to a patient.

This application is related to a concurrently filed copending patentapplication. This patent application is U.S. Ser. No. 07/852,616,entitled "Restrictor Fitting for an Infusion Pump," which application ishereby incorporated herein by reference,

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to medical fluid infusionsystems for delivering a selected medical fluid to a patient, and moreparticularly to an improved apparatus and method for quickly and easilyclearing small quantities of detected air or gas from the detectionfield of an air-in-line sensor in a patient fluid infusion system.

Medical fluid infusion systems are generally known in the art for use indelivering one or more selected fluids through appropriate tubing and/ora catheter or the like to a patient. Such infusion systems often utilizea relatively compact electronically controlled pump adapted for mountingonto a conventional portable medical equipment pole and including anappropriate pump element or elements for closely regulating fluiddelivery to the patient. One example of an infusion pump of this generaltype is marketed by MiniMed Technologies of Sylmar, Calif. under thename MiniMed III.

Modern infusion pumps used in patient fluid infusion systems arecommonly equipped with an air-in-line sensor for monitoring fluiddelivery through a length of tubing and to activate an alarm and/ordisable the pump upon detection of air. In this regard, ultrasonicdetectors are known in the art and have the capability to determine thevolume of air in a tubing line and to activate the alarm or halt pumpoperation when the detected air volume exceeds a predetermined andpotentially harmful threshold. Such air detectors may operate inconjunction with the pump to decrement an accumulated fluid infusionrecord in accordance with the volume of air bubbles detected in theinfusion tubing line.

Relatively small air or gas bubbles may commonly occur at the dischargeside of the pump element, apparently as a result of outgassing at thatlocation. Accordingly, the detection field of the air-in-line sensor istypically located at the discharge side of the pump element to insuredetection of air within the infusion line. In most instances, the volumeof air or gas present at the discharge side of the pump is sufficientlysmall such that no significant patient hazard results and there is noneed to interrupt pump operation. Instead, the threshold setting for theair-in-line sensor is simply adjusted to allow continued pump operationwhen small air volumes are detected.

In some instances, however, small air bubbles can temporarily stickalong the tubing line without obstructing continued fluid flow to thepatient. When this occurs within the detection field of the air-in-linesensor, the sensor will detect the small bubble or bubbles as anelongated and thus significantly greater air volume, whereby the sensorwill respond to activate the alarm or to halt pump operation. In thisevent, it is necessary for nursing personnel or the like to conduct avisual check of the infusion system and, if the actual volume ofdetected air or gas is medically insignificant, manipulate the infusiontubing and/or the pump element to clear the air from the detection fieldof the sensor so that the pump can be restarted. Such manipulation ofthe infusion tubing typically involves manual tapping or shaking of theinfusion tubing line and/or pump components connected thereto todislodge and move stuck air bubbles to a location downstream of theair-in-line sensor. False alarms of this type can occur on severaloccasions throughout the course of a nursing shift, and are viewed bynursing personnel as a significant nuisance.

The present invention provides a significant improvement in medicalfluid infusion systems by adapting the infusion pump for rapid clearingof small quantities of air or gas from the detection field of anair-in-line sensor, without requiring significant manual handling ofsystem components.

SUMMARY OF THE INVENTION

In accordance with the invention, an infusion system for infusing amedical liquid or liquids to a patient includes a "clear air" key orswitch which can be actuated by medical personnel when required to cleara small bubble or bubbles of air or gas from the detection field of anair-in-line sensor. The "clear air" key, when actuated, operates theinfusion pump to deliver a small output pulse of the medical liquid fordislodging the air or gas from the detection field of the air-in-linesensor by displacing the gas to a downstream location along a length ofinfusion tubing.

In the preferred form, the infusion pump includes one or more pumpelements adapted for controlled delivery of one or more medical fluidsfrom a respective reservoir source to a patient, wherein each pumpelement includes an air-in-line sensor such as an ultrasonic airdetector for monitoring air or gas along the infusion tubing at adischarge side of the pump element. The air sensor is designed foradjustable response in accordance with the detected quantity of air orgas to activate a pump alarm and/or to disable pump operation. Forexample, the air sensor can be calibrated to activate the alarm onlyupon detection of a predetermined minimum air volume, or to activate thealarm in conjunction with pump disablement upon detection of a higherpredetermined maximum air volume. One example of a fluid infusion pumpof this type is marketed by MiniMed Technologies of Sylmar, Calif. underthe name MiniMed III.

In accordance with the invention, the infusion pump includes the "clearair" key for selective actuation by medical personnel to clear a smallquantity of air from the detection field of the air sensor when the pumpis in an alarm or stop mode. The "clear air" key is particularlyintended for quickly and easily clearing a small air bubble or bubbleswhich have become stuck within the sensor detection field and have beenmisinterpreted by the sensor as a larger and potentially harmful airvolume. Actuation of the "clear air" key operates the infusion pump todeliver a small volume pulse or bolus of infusion liquid to displace thesmall air volume to a downstream location beyond the sensor detectionfield, so that the normal pump infusion operation can be restarted. Inthe preferred form, the "clear air" key is enabled whenever the sensordetects the predetermined minimum volume of undissolved gas along theinfusion line, whereupon the "clear air" key can be actuated a selectedmultiple number of times to dislodge the air or gas from the detectionfield of the air sensor, while including the fluid pulse or pulseswithin an accumulated infusion record.

Other features and advantages of the present invention will become moreapparent from the following detailed description, taken in conjunctionwith the accompanying drawings which illustrate, by way of example, theprinciples of the invention.

DESCRIPTION OF THE DRAWINGS

These and other advantages of the present invention are best understoodwith reference to the drawings, in which:

FIG. 1 is a front perspective view illustrating a medical fluid infusionpump adapted to include a clear air function embodying the novelfeatures of the invention;

FIG. 2 is an enlarged and fragmented front elevational view of theinfusion pump of FIG. 1;

FIG. 3 is a further enlarged and somewhat schematic sectional depictionof an air bubble disposed within the detection field of an air-in-linesensor;

FIG. 4 is a flow chart depicting operation of the infusion pump clearair function, in accordance with the invention;

FIG. 5 is a front elevational view of a control panel for the infusionpump of FIGS. 1 and 2, with the control panel illustrating normal pumpoperation for delivering fluid via multiple pump channels;

FIG. 6 is a front elevational view of the pump control panel similar toFIG. 5, but depicting one pump channel in an alarm mode and another pumpchannel in a stop mode;

FIG. 7 is a front elevational view of the pump control panel and showinginstructions or prompts for restarting a pump channel from an alarmmode; and

FIG. 8 is a front elevational view of the pump control panel and showingprompts for restarting a pump channel from a stop mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in the exemplary drawings, a medical fluid infusion systemreferred to generally in FIG. 1 by the reference numeral 10 is providedfor delivering one or more medical liquids to a patient (not shown)under controlled, closely regulated conditions. The infusion system 10includes an infusion pump 12 for delivering the medical liquid orliquids through infusion tubing 14 to the patient. The infusion pump 12is designed, in accordance with the invention, to include a "clear air"key or switch which can be manually actuated by medical personnel todeliver a small fluid pulse from the pump, for purposes of clearing asmall quantity of air from the detection field of an air-in-line sensor.

FIGS. 1 and 2 illustrate the infusion pump 12 in the form of a compactinstrument adapted for mounting onto a conventional medical equipmentpole 16 by means of an appropriate adjustable clamp bracket 18 or thelike. The illustrative infusion pump 12 includes multiple parallel fluiddelivery channels for independent programming control to regulateadministration of one or more medical liquids from appropriatereservoirs 20 via the infusion tubing 14 to a patient. Electroniccontrol components and associated mechanical pumping devices areintegrated into the pump 12 and normally operated upon connection of theinstrument to an appropriate power supply as by means of a power cord22. In a preferred form, the infusion pump 12 comprises a compact andmultiple channel pump adapted for operation with disposable pumpelements or cassettes 24, of the type utilized in the MiniMed III fluidinfusion pump marketed by MiniMed Technologies, Sylmar, Calif. A moredetailed disclosure of the construction and operation of the MiniMed IIIpump is found in U.S. Pat. No. 5,000,663, which is incorporated byreference herein.

In a fluid infusion pump 12 of this general type, each pump element 24is normally associated with an air-in-line sensor 26 for monitoring theliquid at the discharge side of the pump element for the presence of airor gas. In this regard, such air-in-line monitoring is necessary ordesirable to prevent infusion of potentially harmful quantities of airor gas into the patient. The air-in-line sensor 26 typically includesoptical or ultrasonic means to detect the presence of undissolved air orgas bubbles in the liquid stream at the discharge side of the associatedpump element 24, and for responding to the detected gas to activate avisual and/or audio pump alarm, and/or to halt operation of thecorresponding pump channel. For example, air-in-line sensors of theultrasound type can be calibrated to place the pump 12 in an alarm modewhen a predetermined, potentially harmful volume of air or gas isdetected, or to place the pump 12 in a stop mode when a largerpredetermined gas volume is detected.

As shown in FIG. 3 with respect to a single pump channel, eachair-in-line sensor 26 comprises a pair of appropriate sensor elements 28mounted on the pump in a position straddling a short length of theinfusion tubing 14 disposed in close proximity to the discharge side ofthe associated pump element 24. Medical fluid in liquid form is normallydischarged from the pump element 24 at a closely regulated rate which ismonitored and recorded by electronic components within the pumpinstrument. Small, medically insignificant quantities of air or gas canoccur in the form of one or more small air bubbles 30 particularly atthe discharge side of the pump element 24 wherein such small volume cannormally be permitted to flow with the infusion liquid through thesensor detection field for ultimate infusion into the patient. Moderninfusion pumps may include the capability to decrement an accumulatedinfusion record in accordance with the volume represented by air or gasbubbles passing through the sensor detection field.

However, it is possible for one or more small air bubbles 30 (FIG. 3) tostick or become trapped along the tubing 14 and within the detectionfield of the air-in-line sensor 26, whereupon such trapped bubble willbe detected by the sensor 26 as a significantly larger gas volume ofelongated shape flowing through the detection field. When this occurs,the air-in-line sensor 26 will erroneously place the pump 12 in an alarmmode or in a stop mode, as appropriate, thereby signalling to medicalpersonnel that the infusion system requires attention. In response,medical personnel such as a nurse will check the infusion system toidentify and remedy the problem. When the alarm is the result of amedically insignificant quantity of air or gas trapped within the sensordetection field, the present invention provides a simple and reliableapparatus and method for dislodging such air or gas from the sensordetection field so that system operation can be quickly and easilyrestarted.

FIG. 4 is a flow chart representing operation of each pumping channel ofthe infusion pump 12 (FIGS. 1 and 2), in conjunction with the apparatusand method of the present invention for quickly and easily clearingsmall quantities of air or gas from the detection field of anair-in-line sensor. FIGS. 5-8 are representative displays for a pumpcontrol panel 32, illustrating the apparatus and method of the presentinvention.

More specifically, with reference to FIG. 4, the infusion system 10 isnormally operated to deliver a medical liquid through a pump element 24and past an air-in-line sensor 26 to a patient. FIG. 5 illustrates arepresentative information display of the liquid crystal type (LCD) forthe control panel 32, particularly with respect to the MiniMed III pumpwhich can be operated to infuse fluid to the patient with simultaneousoperation of three parallel pumping channels identified by the letters"A", "B" and "C". Each channel can be individually programmed by medicalpersonnel for independent operation in accordance with the specificmedical fluids and the requirements of the patient.

When a threshold quantity of undissolved air or gas is detected withinthe detection field of the air-in-line sensor associated with one of thepumping channels, that sensor 26 signals the pump 12 to place thepumping channel in an alarm mode. FIG. 6 illustrates the pump controlpanel 32 indicating visually that channel "A" is in an alarm mode. Anaudio alarm is normally provided to generate a distinctive signalindicative of alarm mode status. Alternatively, if the detected air orgas volume is a higher predetermined quantity, the air-in-line sensorcan signal the pump 12 to place the corresponding channel in a stopmode, as indicated by the control panel 32 in FIG. 6 with respect topumping channel "B". In the stop mode, infusion pump operation for theassociated channel is halted, typically in conjunction with activationof the audio alarm, as noted above.

When one of the pumping channels of the infusion pump 12 is in the alarmor stop modes, the pump alarm functions insure prompt attention bynursing or other medical personnel to resolve the problem so that normalpump infusion operation can be promptly resumed. As noted above, theproblem may be attributable to an insignificant quantity of air or gastrapped within the detection field of the air-in-line sensor.Confirmation of such cause can be made rapidly by medical personnel uponmere inspection of the infusion tubing 14 within the sensor detectionfield. When this cause is present, it is necessary to clear the stuckbubble or bubbles from the detection field so that normal pump operationcan be resumed.

FIG. 7 shows a control panel display which is presented upon depressionof a master key 34 associated with pumping channel "A", when pumpingchannel "A" is in the alarm mode as depicted in FIG. 6. The paneldisplay shown in FIG. 7 provides prompts or instructions to medicalpersonnel for resolving the cause of the alarm and for restarting pumpoperation. One preferred resolution, particularly if an insignificantquantity of air or gas is present at the sensor 26, is to depress a"clear air" key 36 on the pump control panel 32. This "clear air" key isenabled when the pump is in the alarm or stop modes, and convenientlyappears in the preferred form as a prompt 37 alongside the key 36 withinthe control panel display screen shown in FIG. 7. Depression of the"clear air" key 36 operates the pump to deliver a small output pulse orbolus at a high rate (typically 999 ml/hr) to the patient. This deliveryof a small pulse of the infusion liquid, preferably about 0.2milliliters or less, is often sufficient to dislodge and displace thetrapped bubble or bubbles to a position downstream from the sensordetection field. However, for most medical infusion fluids and/or mostpatients, the delivery of the small output pulse is not a sufficientvariation from the programmed fluid delivery rate to present any medicalconcerns.

Subsequent to depression of the "clear air" key 36, and following theinstructions on the display panel 32 (FIG. 7), a pump start key 38 isdepressed by the medical attendant in an attempt to restart normal pumpoperation. If the detected air or gas has been dislodged from the sensordetection field, such depression of the start key 38 will return thedisplay information to the previous screen, for example, the normaloperation screen of FIG. 5 if no other channels are in the alarm or stopmodes. The attendant can then press a quiet key 40 to clear the audioalarm function (FIG. 7).

If depression of the start key 38 fails to restart normal pumpoperation, this failure is due to continued presence of the air or gasbubbles within the detection field of the air-in-line sensor 26. In thiscondition, the pump 12 can be programmed to enable or permit depressionof the "clear air" key 36 a second time and/or a selected additionalnumber of times to deliver one or more additional small fluid pulsesfrom the pump. For example, in a typical adult patient and medicalinfusion environment, the pump 12 is preferably programmed to permitdepression of the "clear air" key 36 up to five or six times in anattempt to dislodge air or gas from the sensor detection field. If thepump is not restarted, despite following of the foregoing procedure,other manual remedial steps can be taken to dislodge the air and torestart the pump. Alternately, manual remedial action can be taken atthe outset of the alarm mode condition, at the option of attendingpersonnel.

FIG. 8 illustrates a similar sequence of remedial steps to be taken whena Dumping channel is in the stop mode, as represented by pumping channel"B" in FIG. 6. Depression of a master key 42 associated with channel "B"activates the panel display 32 shown in FIG. 8, with appropriateinstructions for depression of the now-enabled "clear air" key 36 toresolve the cause of channel stoppage. The clear air key can bedepressed one or more times, with such depression followed bycorresponding attempts to restart the infusion pump by depression of thestart key 38. Once again, if this procedure fails to restart the pumpdue to continued detection of air at the sensor detection field, the aircan be dislodged following traditional manual procedure.

The present invention thus provides a relatively simple apparatus andmethod for quickly and easily dislodging small quantities of air stuckwithin the detection field of an air-in-line sensor in a medical fluidinfusion system. Such detected air or gas is dislodged and moved fromthe sensor detection field by delivering one or more small pulses of theinfusion fluid from the pump. While the pump is normally adapted formaintaining an accumulated fluid infusion record to track the quantityand rate of fluid infusion to a patient, and detected volumes of air orgas may be decremented from this infusion record, the pump can befurther programmed to add to the infusion record each small fluid pulsedelivered upon depression of the "clear air" key 36.

A variety of modifications and improvements to the invention describedfurther herein will be apparent to persons skilled in the art. Forexample, while the invention is shown with respect to a programmablepump 12 having a sequence of control panel screens associated withbutton keys or switches which may have different functions according tothe control panel screen being displayed, it will be understood that the"clear air" key and its associated clear air function can be embodied indifferent pump configurations such as the provision of a dedicated"clear air" key. Accordingly, no limitation on the invention is intendedby way of the foregoing description and accompanying drawings, except asset forth in the appended claims.

What is claimed is:
 1. A medication infusion pump, comprising:pump meansfor delivering a selected therapeutic liquid to an infusion line undercontrolled flow conditions for infusion to a patient; an air-in-linesensor associated with said pump means, the air-in-line sensor having adetection field configured to receive a short length of the infusionline and comprising means for detecting gas bubbles within the shortlength of infusion line, and alarm means for responding to a detectionof gas bubbles within the infusion line by said means for detecting toactivate an alarm; and manually actuated means for operating said pumpmeans to deliver an output pulse of the therapeutic liquid to the shortlength of the infusion line to dislodge and move gas bubbles detectedwithin the detection field along the infusion line to a positiondownstream of the detection field.
 2. A medication infusion pump asdefined in claim 1, wherein said air-in-line sensor comprises:means forgenerating an alarm signal in response to detection of a predeterminedgas volume;and wherein said alarm means is activated in response to saidalarm signal, for enabling the manual actuation of said manuallyactuated means at least one time whenever said alarm means is activated.3. A medication infusion pump as defined in claim 2, wherein said pumpmeans additionally comprises:means for limiting the number of times saidmanually actuated means can be actuated.
 4. A medication infusion pumpas defined in claim 1, wherein said pump means comprises:a housing witha control panel thereon, said manually actuated means comprising adepressible key located on said control panel.
 5. A medication infusionpump as defined in claim 1, wherein said pump means comprises:means formaintaining an accumulated fluid infusion record, said pump meansfurther comprising means for adding each output pulse delivered fromsaid pump means to said record.
 6. A medication infusion pump,comprising:programmable pump means for delivering a selected medicalliquid to an infusion line under controlled flow conditions for infusionto a patient; air-in-line sensor means, associated with said pump means,for detecting undissolved gas within the infusion line, said sensormeans having a detection field configured to receive a short length ofthe infusion line, and the sensor means also for activating an alarmwhen the amount of undissolved gas detected within said detection fieldexceeds a predetermined minimum volume; and said pump means furthercomprising manual switch means for operating said pump means to deliveran output pulse of a predetermined volume of the medical liquid to theinfusion line to dislodge and move undissolved gas through the infusionline to a position downstream of the detection field.
 7. A medicationinfusion pump as defined in claim 6, additionally comprising:means forenabling actuation of said manual switch means at least one timewhenever said alarm is activated.
 8. A medication infusion pump asdefined in claim 7, further comprising:means for selectively limitingthe number of times said manual switch means can be actuated to deliversaid output pulse.
 9. A medication infusion pump as defined in claim 6,wherein said pump means comprises:means for maintaining an accumulatedfluid infusion record, said pump means further comprising means foradding each output pulse delivered from said pump means to said record.10. An infusion system for delivering a selected medical liquid to apatient, said system comprising:an infusion line; an infusion pumpoperating on the infusion line for delivery of a medical liquid throughsaid infusion line to the patient under controlled flow conditions; anair-in-line sensor, associated with said infusion pump, said sensorhaving a detection field engaged with a short length of said infusionline, said sensor comprising means for detecting when a volume ofundissolved gas is present within said short length of the infusion lineand for generating an air-in-line signal when the volume of undissolvedgas is detected by the means for detecting and exceeds a predeterminedminimum level; alarm means responsive to said air-in-line signal toindicate that a volume of undissolved gas exceeding the predeterminedminimum level has been detected within said short length of the infusionline; and manual switch means for operating said pump to deliver atleast one small output pulse of the medical liquid to said infusion lineto dislodge and move the volume of undissolved gas to a positiondownstream of said detection field.
 11. An infusion system as defined inclaim 10, wherein said alarm means comprises:means responsive to saidair-in-line signal to halt operation of said pump.
 12. An infusionsystem as defined in claim 10, wherein said sensor comprises:means forgenerating a first air-in-line signal when the volume of the undissolvedgas exceeds said predetermined minimum level, and a second air-in-linesignal when the volume of the undissolved gas exceeds a higherpredetermined maximum level, said alarm means being responsive to saidfirst signal to activate an alarm indicator, said alarm means beingresponsive to said second signal to halt operation of said pump.
 13. Aninfusion system as defined in claim 10, further comprising:means forenabling manual operation of said manual switch means at least one timewhen said alarm means indicates that the volume of undissolved gaswithin said short length of the infusion line has been detected.
 14. Aninfusion system as defined in claim 10, further comprising:means forselectively limiting the number of times said manual switch means can beoperated to deliver said output pulse.
 15. An infusion system as definedin claim 10, wherein said pump comprises:a housing with a control panelthereon, said manual switch means comprising a depressible key locatedon said control panel.
 16. An infusion system as defined in claim 10,further comprising:infusion record means for maintaining an accumulatedrecord of medical liquid delivered to the patient, said infusion recordmeans comprising means for adding each output pulse to said record.